The present invention relates to closure devices. More particularly, the present invention concerns a closure device for fermentation vessels which permits access to the vessel
Fermentation processes are employed for a wide variety of commercially important products ranging from food products to pharmaceuticals. Often in the development of a fermentation process, new strains of microorganisms are isolated and identified which improve a known process or produce a new and useful fermentation product. The isolation of pure strains of microorganisms is a detailed process which involves many steps. Typically, a newly identified colony of a microorganism is first transferred from a Petri dish culture to a test tube containing appropriate nutrients. This culture is often transferred one or more times to new culture tubes until the culture is free of contamination by other undesired strains of microorganisms. These transfers are typically effected by means of a transfer loop which is inserted into the mouth of the culture tube after removing the culture tube closure. Good laboratory practice dictates that both the mouth of the culture tube and the closure be sterilized by flaming prior to replacing the closure on the tube.
Once a pure strain of the desired microorganism has been prepared in a test tube, the culture is typically transferred to a closed shake flask containing a sterile liquid culture medium. The medium is inoculated with the microorganism and placed on a shaking table in an incubator at a temperature and for a period of time sufficient to permit growth of the microorganism culture. During this stage of the process, it is frequently necessary to add materials to the culture medium or to remove aliquot samples from the shake flask for analysis. As before, good laboratory practice requires flame sterilization of the flask mouth and closure before reclosing the flask after each such access to the flask contents. All of these operations require two-hand manipulation of the flask, the closure, and a transfer loop or pipette which can be cumbersome. Moreover, the recent widespread introduction of plastic disposable shake flasks has complicated the step of flame sterilization.
The vast majority of microorganisms useful in commercially viable fermentation processes belong to the class of aerobic microorganisms; that is, microorganisms which require oxygen to carry on their metabolic processes. In fact, the very purpose of shaking or stirring fermentation broths is to ensure effective mixing of air with the liquid culture medium. As a result, any closure device employed in the culturing of aerobic microorganisms must permit the passage of air into the vessel and the exchange of gaseous fermentation products out of the vessel while maintaining the sterility of the vessel contents.
In the past it has been the widespread practice to close fermentation test tubes, flasks, shake flasks, and other small laboratory scale fermentation vessels with a porous closure such as a plug of sterile cotton or similar porous material made of a synthetic material such as foamed polyethylene or polypropylene. More recently stainless steel and plastic cap closures have become available which fit over the mouth of the fermentation test tube or flask, permitting the passage of gases into and out of the fermentation vessel. Examples of such closures are KIM-KAP.TM. closures, available from Owens-IL, and KAP-UTS.TM. plastic closures and BELLCO stainless steel closures available from Bellco Technology, P.0. Box 340, Erudo Road, Vineland, NJ 08360. These closures are of a diameter slightly larger than the neck of the fermentation tube or flask and fit snugly over the mouth of the test tube or flask by means of fingers or ridges on the inside vertical walls of the closures. Small stand-offs inside the the closures prevent the seating of the top of the closure against the top of the fermentation tube or flask, thus permitting the passage of gases into and out of the tube while maintaining the sterility of the vessel contents.
A disadvantage of these prior art closures, whether of the porous plug type or the snug-fitting cap closure type, is the need to remove the plug or closure each time access to the fermentation vessel contents is required. Each removal of the closure provides the potential for contamination of the vessel contents and requires flaming of the vessel mouth and closure to ensure sterility.
Thus there is a need in the fermentation art for a closure device which permits direct access to fermentation vessel contents without the need to remove the closure device.